[Thecastle]

If your burning that much oil your misfires are probably from having clogged cats. The leaded gas didn’t help the cats. You need to find the source of your oil consumption, before replacing the cats (temp fix would be to remove them)

Typically oil loss sources are
Big leak
Bad valve stem seals
Bad ccv system
Bad turbos
Bad cylinders aka scored bores from carbon build up or broken piston rings.
Blown head gasket (not common)

p.s. we had a ford years ago that was a 2-stroke lol (they all start as 4 strokes). It burned a quart of oil every 10 gallons of gas. The cat totally plugged so we had to gut it to get it to run right. That was a fine car, the only difference between 1/4 throttle and full throttle was the amount of smoke...